<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <style>
      .parent{
        width: 200px;
        height: 200px;
        background-color:skyblue;
        display:flex;
        align-items:flex-start;
      }
      .parent div{
        width: 50px;
        height: 50px;
        background-color: green;
      }
      .parent .first{ 
         align-self:flex-end; /*可以定义与其他盒子不同的样式(auto,flex-end,flex-start,center,baseline,stretch) */
                              /* auto是继承父元素的对齐方式属性,其他的都是覆盖align-items */
      }
      .parent .second{
        align-self:auto; /*对齐方式不改变*/
      }
      .parent .third{
        height:auto;  /*stretch只在高度未设置或者高度为auto的时候起作用*/
        align-self:stretch;
      }
  </style>
</head>
<body>
  <div class="parent">
      <div class="first">1</div>
      <div class="second">2</div>
      <div class="third">3</div>
      <div>4</div>
  </div>
</body>
</html>